The low-carb Paleo and ketogenic diets can improve performance for triathletes and other endurance athletes. (Getty Images)

While carb-loading is deeply ingrained in endurance sports, a growing number of long-distance runners, cyclists and triathletes have experienced performance gains with the low-carb Paleo and ketogenic diets.

A two-year study recently conducted by scientists at Cambridge University and Umeå University in Sweden showed the Paleo diet is twice as effective for producing weight loss and melting body fat as low-fat diets.

Tim McGraw lost 40 pounds and got rippling abs at age 48 with a low-carb Paleo diet and CrossFit.

“Clinical trials have shown the Paleo diet is the optimum diet that can lower the risk of cardiovascular disease, blood pressure, markers of inflammation, help with weight loss, reduce acne, promote optimum health and athletic performance,” said Loren Cordain, author of The Real Paleo Diet Cookbook.

Joe Friel, a U.S. Olympic triathlon coach, said the Paleo diet works for triathletes because it helps with recovery.

Joe said the Paleo menu provides more antioxidants and vitamins than the typical high-carb diet favored by most endurance athletes and boosts fat oxidation and weight loss — a major advantage for endurance athletes, because the less excess weight you carry, the faster you’ll be.

Low-Carb Ketogenic Diet Used By Ironman Triathletes

Another interesting trend is the growing use of the high-fat, low-carb ketogenic diet among triathletes.

Fitness expert Ben Greenfield trained for the 2013 Ironman Triathlon World Championships by following the ketogenic diet and completed the epic endurance race in an impressive 9:59:26.

Ben, author of the bestseller Beyond Training, detailed his ketogenic diet experiment on his blog. Greenfield’s breakfast the morning of the Ironman was a half-stick of butter, two shots of MCT oil, and a cup of coffee — a stark contrast to the heaping plates of pasta most endurance athletes inhale before a race.

Similarly, Dr. Jay Lehr, a 79-year-old triathlete, has followed a low-carb, high-fat ketogenic-style diet his entire life and credits it for his excellent health.

Jay Lehr, a 79-year-old triathlete, has followed a ketogenic-style diet his entire life.

Jay has thrived on a diet of red meat, saturated fat, dairy, eggs, butter, and lard and has never felt better, as Celebrity Health & Fitness previously reported.

“I’ve never been inside a regular doctor’s office,” said Lehr. “I have lived my entire life on high fat — dairy, eggs, butter and lard.”